They are most commonly called livestock panels and are widely available in the states as fencing...as far as I know, only Tractor Supply calls them a 'feedlot panel'. Wait--make that widely available in most rural and quasi-rural areas, in the states. Pretty much all the farm, feed, and building supply stores carry something along those lines.
There are different styles--cattle panel, hog panel, sheep/goat panel, horse panel, utility panel, etc. They are generally a galvanized welded rod panel and differ primarily in the overall height of the fence and the size and arrangement of the openings--the mesh. Hog panels are only 34" tall with a graduated mesh--2", 3" at the bottom up to 6" at the top. Horse panels typically have a uniform 2" mesh. Most are 4 gauge wire (except the 'heavy duty' versions are 2 and 3/4 and there is also a 1 gauge bull panel, which would be practically impossible to wield), dang sturdy and durable and they make great fences--I personally prefer them over chainlink for residential dogs, too
There are a few different versions of 6 gauge with uniform 4" or 6" mesh, which I think would be plenty sturdy enough and a bit easier to work with. (For example, I might be inclined to get either a 5' or 8' tall, 20' long panel for two wider arbors, if it were me.)
Certainly, the gauge and size can be customized as well, and there are a few US manufacturers as well as Chinese manufactures willing to help you contain your elk or buffalo as needed, but I don't know how affordable a custom arch plus shipping might be
I don't know what you have access to in St. Croix, but maybe there are some other welded wire galvanized fencing materials that could work, too? If you can find a sturdy gauge (6, 5, 4) in a long enough length (in my experience, most stuff sold in a roll would not be suitable to support itself or anything else when bent into an arbor, whereas the stuff sold as panels would be, if you can get them long enough).
Alternatively, there are a variety of rather affordable welded wire products for concrete (concrete mesh) that might be easier to come by and work very well for tomato cages, trellises, and arbors or whatnot, if you don't mind the rusted look...
edited to say--kind of a lot of words to say what he just said--but both Lowes and HomeDepot do carry "cattle panels" and I don't think of them as a farm supply store. You will likely find a better variety and quality (IMO) at a farm supply store.
